ilog2: return unsigned int for applicable routines
ilog2: return unsigned int for applicable routines

For the routines where we can't return a negative value, return an
unsigned value.

Signed-off-by: H. Peter Anvin <8a453bad9912ffe59bc0f0b8abe03df9be19379e@linux.intel.com>

techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm